The increased complexity of aircraft jet engine hydraulic and pneumatic control systems has resulted in weight and cost increases and reliability decreases. To improve such systems, U.S. Pat. No. 5,551,478, assigned to the assignee of the present invention has issued which is directed to a hydraulic control network which uses a latching valve. As a result of this system, an electro-mechanical-hydraulic mechanism is provided which has resulted in an improvement over the conventional systems.
The increased complexity of current control systems for aircraft engines stems at least partly from an increase in the number of mechanical variables or functions on an aircraft jet engine which must be controlled either hydraulically or pneumatically The mechanical variables, such as the engine bleed, are typically controlled by hydraulic or pneumatic actuators that, in turn, are controlled by fuel or air actuator valves.
The control system of U.S. Pat. No. 5,551,478, is designed to operate under the command of an engine control of the aircraft jet engine which is electronic in nature and issues command signals to a pair of torque motors of the system. The first torque motor of the system acts in conjunction with a three position hydraulic valve. A second torque motor operates in conjunction with a second hydraulic valve to control the linear position of the spool of a multiplexer selector valve. The multiplexer selector valve is a 2.times.12 valve in that the valve spool is linearly translatable between twelve different positions. In each of the twelve positions, it is possible to generate two high pressure signals to a pair of two position, on/off latching hydraulic fuel and/or air actuator valves. Each actuator valve requires a high pressure signal to turn it on an another high pressure signal to turn it off. Thus, a total of twelve actuator valves are controlled in one embodiment of the control system. The position of the multiplexer selector control valve spool is fed back to the electronic control via a linear variable differential transducer (LVDT).
Currently available electronic controllers are not operable to properly control system of U.S. Pat. No. 5,551,478. That is, current controllers and methods for controlling are not designed to optimize the benefits of the control system disclosed in this patent.
There exists a need, therefore, for an improved controller and method of controlling a hydraulic control system, and more specifically, a hydraulic control system which uses a multiplexing hydraulic control network and latching valves.